drm/amd/display: Return max resolution supported by DWB

mode_config's max width x height is 4096x2160 and is higher than DWB's
max resolution 3840x2160 which is returned instead.

Cc: stable@vger.kernel.org
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd: include drm/drm_edid.h only where needed

Including drm_edid.h from amdgpu_mode.h causes the rebuild of literally
hundreds of files when drm_edid.h is modified, while there are only a
handful of files that actually need to include drm_edid.h.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: Create amdgpu_dm_wb_connector

[WHY]
We need to track the dc_link and it would get confusing if
re-using the amdgpu_dm_connector.

[HOW]
Creating new amdgpu_dm_wb_connector.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drm/amd/display: Initialize writeback connector

[WHAT]
Create a drm_writeback_connector when connector signal equals
SIGNAL_TYPE_VIRTUAL.

Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>